Synthesis of novel azo linkage-based Schiff bases including anthranilic acid and hexanoic acid moieties: Investigation of azo-hydrazone and phenol-keto tautomerism, solvatochromism, and ionochromism

Two new azo-Schiff base receptors (L1 and L2) containing azo and azomethine groups with a conjugated group (benzyl ring of anthranilic acid, in L1) and electron-donating group (alkyl chain of hexanoic acid, in L2) were synthesized and characterized. Azo-hydrazone/phenol-keto tautomerism and solvatochromism were investigated. Studying their sensing ability towards cations (Co2+, Cu2+, Zn2+, Ni2+, Pb2+, Cd2+, Mn2+, Fe3+, Cr3+, and Al3+), high sensitivity and selectivity were recorded for Fe3+ by naked eye and UV-Vis spectra in DMF-aqueous HEPES buffer (v:v, 1:1, pH 6.8). The color of L1 and L2 solutions instantly changed from yellow to deep orange and pale orange. L2 sensed Cu2+ and Al3+ ions selectively by UV-Vis spectra.